Which? testing reveals safety concerns about popular face mask brands

New Which? research indicates alarming flaws in the effectiveness of widely-available face coverings, with one popular reusable mask only blocking a third of potentially harmful particles during testing.

The consumer champion looked at a range of popular brands and styles of face coverings and masks, including those sold by pharmacy chains, supermarkets, high street stores and online retailers. Scientists tested for how well they filtered particles, how breathable they were, and how they fared after multiple washes.

Which? found that the best performing face covering was able to block more than 99 per cent of potentially harmful bacterial particles, filtering just as well as a disposable mask, but the worst product only trapped a third of the particles passing through.

Worryingly, some of the face coverings with high filtration claims on the packet did not live up to them in Which? testing, and seven of the 12 had poor packaging instructions that failed to provide key information for maximising effectiveness and protecting the wearer.

The Adidas face covering (£17 for a pack of three), sold at retailers including ASOS, Next and Sports Direct, only filtered a third of particles in Which?’s tests, while the Vita Shield face covering (£9.99 for 3) dropped from 60 per cent filtration on first use to 38 per cent after five washes.

Adidas told Which? its mask was designed early on in the pandemic, before there were defined performance criteria for non-medical face coverings, and that its mask was tested for comfort and breathability.

The Vita Group said its face covering had been tested at external accredited testing facilities, which showed filtration levels of more than 90 per cent. It said that the discrepancies in results demonstrate the need for mandatory, overarching standards to be put in place.

The highest-scoring face covering tested was the Which? Best Buy Airpop Pocket (£24.99 for 4), available direct from Airpop or on Amazon. The covering is made from similar materials to disposable masks and does a superb job of filtration – though it is “semi-reusable,” so can only be washed and reused a set number of times before it needs to be binned.

Which? also awarded Best Buys to face masks from Superdrug (£4.99 for 3), The Big Silk (£16.90 for 1) and Marks & Spencer (£9.50 for 5). These masks strike the balance between filtration and breathability well, and testers found them comfortable to wear.

The NEQI reusable face mask (£15 for 3), which is available from retailers including Boots and Ocado, as well as Bags of Ethics Great British Designer face coverings (£15 for 3), available at Sainsbury’s, Argos or Waitrose, both remain Which? Best Buys.

Some reusable face masks now display high filtration levels on the packet, but four of those did not achieve the stated levels when tested by Which?.

The Wise Protec (£10 for 1), sold at John Lewis, Matalan and Home Bargains, and Alvita (£7 for 2) mask, sold at Boots, both claim more than 90 per cent filtration efficiency, but Which? tests showed lower levels, at 80 per cent and 82 per cent respectively. After washing, this dropped to the high 60s for both.

Boots’ Adult Reusable Face Mask (£10 for 2) claims more than 95 per cent filtration, which was borne out in initial tests, but after five washes this dropped to 75 per cent.

Wise Protec and Alvita told us that their above 90 per cent filtration levels had been verified in independent, accredited labs. Boots also said its mask had been “rigorously tested”.

Some of the masks Which? tested are ‘semi-reusable’. They are made from similar materials to disposable masks, but can be worn and washed a set number of times before they have to be thrown away.

Of these, the Airpop Pocket mask lived up to its filtration claims and still performed well after multiple washes. But the Alvita reusable barrier mask, sold at Boots, had a drop in filtration to 66 per cent after a few washes (below Which?’s minimum filtration threshold) and was not very comfortable to wear.

Seven of the 12 products Which? tested also had poor usage and washing instructions on the packaging, both of which are key for maximising effectiveness, as poor mask hygiene could increase your risk of infection.

Which? looked for basic information on the packet, like detailed cleaning instructions including washing method, frequency and temperature. Researchers also expected to see clear warnings about how to correctly wear the mask, and confirmation that it was not a medical device.

Voluntary minimum performance requirements are in place for reusable face coverings, but the discrepancies revealed by Which? results show that plenty still aren’t up to scratch.

The consumer champion has been involved in the development of industry standards for non-medical face coverings in the UK, and believes there’s a need for more stringent oversight of non-medical face coverings so that consumers can be assured that minimum filtration and safety standards are met.

Which?’s testing shows that reusable face coverings can be highly effective, but it is currently hard for consumers to know what they are getting.

In the meantime, consumers can:

  • Carefully research their options with our independent reviews and advice
  • Remember that a good, snug fit around the face is crucial
  • Replace masks when they are looking worn or don’t fit well anymore
  • Pay attention to mask hygiene: wash your hands or use sanitiser before putting on or removing, and avoid touching the front of the mask, store in a bag and wash regularly

Harry Rose, Which? Magazine Editor, said:

“Face coverings not only need to be durable and comfortable, but also provide effective filtration in order to keep us and others safe.

“Our tests show there is still work to be done to improve the quality of face coverings. While the best reusable face coverings can be just as effective as a disposable mask, there are still too many that fall short of the mark.

“We would like to see more manufacturers committing to minimum performance standards for filtration and ensuring basic safety instructions are present, but for now it is worth taking time to research the best option for yourself and your loved ones before buying.”

Notes to editors

Full results table

NB. Star ratings shown are a selection of key test results, not an exhaustive list. Each star rating represents a range of data points, and different tests are subject to different weightings and / or limits, which is why some masks may have similar star ratings but different overall scores.

How Which? tested the face coverings

Filtration efficiency

We followed the industry standard method for assessing mask bacterial filtration efficiency, which determines how effective a face mask is at blocking particles, using bacteria as a proxy. This is the same test used to assess surgical masks for efficiency.

Tiny bacterial particles (three micrometres in diameter) are shot through the face covering via an aerosol generator at a flow rate of 28 litres per minute.

Filtration efficiency is measured based on the percentage of colony-forming units of bacteria that were able to pass through the face covering.

We repeated the test after five washes.


To find out how easy or hard it will be to breathe in a face covering, we measure the pressure required to draw air through the mask at a rate of eight litres per minute.

We also repeated breathability tests after five washes.

Cleaning and harness strength

Three people with different head shapes and sizes put each of the coverings on and then took them off again 80 times to simulate a month’s worth of wear, looking for signs of damage.

No damage was reported to any of the coverings during this test, apart from the Vita Shield where the material started to fray slightly after repeated putting on and removing.

Ease of use

  • Which? checked a range of ease of use measures, including:
  • How easy it is to put the face coverings on and take them off
  • How they felt to wear: looking for tightness, gaps and ease of adjustment
  • Comfort while talking
  • How much they make your glasses fog up

How to buy a face mask video.

YouTube URL: https://www.youtube.com/watch?v=DIMwIgW2b7s

Should you wish to include a linkback in your copy, the following links will go live when the embargo lifts:

Main face masks news story: https://www.which.co.uk/news/2021/05/reusable-face-coverings-can-be-highly-effective-which-tests-reveal/

Face masks full results page (already live, will be updated with new results on 19/05/21): https://www.which.co.uk/reviews/face-masks/article/best-reusable-face-masks-awLeA3A6XoZD

How to choose a reusable face covering

Go for multiple layers – our tests showed a clear difference between single-layer face coverings and those with a double or triple layer.

Make sure it’s adjustable, or comes in different sizes – our testers rated face coverings higher for fit and comfort when they were adjustable, either by the ear loops and mouldable nose wire, or because the mask came in different sizes. Find out more in our face mask buying guide.

Be wary of antimicrobial coatings – these usually come with caveats such as only lasting for a set number of washes, and may take several hours to kill germs. Buy from reputable retailers and do your research. You can check OEKO-TEX fabric safety certifications here: https://www.oeko-tex.com/en/label-check

For more info: https://www.which.co.uk/news/2021/04/under-armour-face-mask-withdrawn-from-sale/

Rights of reply

Adidas statement

“Our face cover was designed for the general public and is not medically graded. It can help limit the spread of droplets, to help protect others from transmissible germs. This is outlined clearly on the consumer-facing product communications. There was not an industry standard for non-medical face coverings at the time of design, but it was comprehensively tested together with our development partners against Adidas’ performance criteria to ensure safe breathability and comfort for wearers.”

A spokesperson for Wise Protec commented:

“We are pleased to have been included in the recent Which face covering tests. We are confident that our masks continue to provide the highest level of anti-bacterial face mask protection. Our unique triple layer anti-microbial social mask has consistently performed above 90% effectiveness in several independent accredited European standard laboratories using multiple testing standards, and we test every batch of our production before release. We are also committed to continuous improvement and we will work to understand the Which? testing protocols and interrogate their results, to ensure that Wise Protec Anti-Microbial Face Masks meet and exceed best in class standards.”

Vita statement

“We are surprised and disappointed by the Which? test results used in these findings. Our decision to simultaneously send our face coverings to external accredited testing facilities to test against CEN CWA17553:2020 provided us with documented evidence of our advertised specifications being met and having been consistent over the last 10 months.”

“The Vita Group stands behind the test results rigorously generated over the last 12 months by Centexbel, a world-renowned independent accredited test centre. Their results bear no relation to the results obtained by Which?, which supports our view that mandatory standards need to be decided by legislation for all face coverings.”

A spokesperson at Alliance Healthcare said:

“The Alvita Barrier Mask claims a “filtration efficiency for 3µm particles > 90%”. That claim is supported by rigorous test data carried out in accordance with industry standards for measuring particulate filtration efficiency by an independent accredited laboratory. BFE is a mandatory test for medical devices, and the Alvita Barrier Mask is not a medical device. There is not currently a mandatory standard test method for reusable face coverings. We have full confidence in the performance and quality of the Alvita Barrier Mask.”

Boots comment:

“We have full confidence in the quality of the filtration claims made on the Boots Reusable Face Masks. The product has been rigorously tested and it continues to achieve 95% filtration for ten washes. The face covering is made from a stretchy lycra to provide maximum comfort to the wearer. In order to maintain the highest quality, we recommend following the washing and drying instructions exactly as stated on the packaging.”

About Which?

Which? is the UK’s consumer champion, here to make life simpler, fairer and safer for everyone. Our research gets to the heart of consumer issues, our advice is impartial, and our rigorous product tests lead to expert recommendations. We’re the independent consumer voice that influences politicians and lawmakers, investigates, holds businesses to account and makes change happen. As an organisation we’re not for profit and all for making consumers more powerful.

The information in this press release is for editorial use by journalists and media outlets only. Any business seeking to reproduce information in this release should contact the Which? Endorsement Scheme team at endorsementscheme@which.co.uk.

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